This study is designed to evaluate the use of thrombolytic enzyme therapy in central retinal vascular occlusion. In both arterial and venous occlusion, streptokinase will be used in doses calculated to produce a systemic fibrinolytic state. In venous occlusion a comparison will be made between the use of heparin and streptokinase in the treatment of this disease. The aim of therapy is the restoration of patency to the occluded vessels and of visual acuity to the affected eye. The efficacy of therapy will be determined by means of tests of visual acuity, funduscopic examination and fluorescein angiography. It is hoped that thrombolytic therapy will prove to be successful in the treatment of this condition and will offer some more definitive approach to this problem.